<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }
    html,body {
      background-color: rgb(235, 230, 230);
    }
    .app {
      display: flex;
      flex-direction: column;
      max-width: 430px;
      margin-left: auto;
      margin-right: auto;
      height: 100vh;
    }
    ::-webkit-scrollbar {
      width: 4px;
      height: 4px;
    }
    ::-webkit-scrollbar-thumb {
      background-color: rgba(0,0,0,.3);
      border-radius: 2px;
    }
    .app .header,
    .app .footer{
      height: 60px;
      flex-shrink: 0;
      background-color: #fff;
    }
    .app .main {
      overflow: auto;
      flex-grow: 1;
      background-color: #c5c2c2;
    }
  </style>
</head>
<body>
  <div class="app">
    <div class="header">头部</div>
    <div class="main">
      <div style="height:1200px">主体</div>
    </div>
    <div class="footer">脚部</div>
  </div>
</body>
</html>